Geology Reference
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where:
d
r
displacement rate (in./min, mm/min)
d
f
estimated horizontal displacement at failure (in., mm)
t
f
total estimated elapsed time to failure (min)
Note 7
—The magnitude of the estimated displacement at fail-
ure is dependent on many factors including the type and the
stress history of the soil. As a guide, use
d
f
= 0.5 in. (12 mm) if
the material is normally or lightly overconsolidated fine-
grained soil; otherwise use
d
f
= 0.2 in. (5 mm).
(5) At the completion of the test, remove the normal force from the
specimen by removing the mass from the lever and hanger or by
releasing the pressure.
For cohesive test specimens, separate the shear box halves
with a sliding motion along the failure plane. Do not pull the shear
box halves apart perpendicularly to the failure surface, since it
would damage the specimen. Photograph, sketch, or describe in
writing the failure surface. This procedure is not applicable to co-
hesionless specimens.
Remove the specimen from the shear box and determine its
water content according to ASTM Test Method D 2216 (Chapter 4).
(6) Repeat the entire procedure for two or more specimens at
different normal loads.
Note
—The test procedure described can be used for each of the three
basic types of test. For an unconsolidated undrained test, follow steps
(1), (3), (5), and (6). For a consolidated undrained test, follow steps (1) to
(3), (5), and (6). For a consolidated drained test, follow steps (1) to (6).
Note
—The foregoing procedure is adapted from ASTM D 3080-98 [1].
Data collected in the direct shear test should include the following:
DATA
[A] Specimen Data
Diameter or side of specimen (in.)
Initial height of specimen (in.)
Mass of specimen at beginning of test (g)
Initial water content data:
Mass of wet soil sample at beginning of test (g)
Mass of oven-dried soil sample (at end of test) plus can (g)
Mass of can (g)
Final water content data:
Mass of wet soil specimen plus can at end of test (g)
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